There are two techniques available for introducing comments into a program. An example of each is shown below.

/* This is a comment. */
// And this is also a comment.

Comments beginning with /* and ending with */ may be extended across multiple lines and may not be nested. The characters /* have no special significance inside a comment bracket.

Comments of the style // extend to the end of the line. Comments of this style may not span multiple lines, except when the preprocessor is used to extend the line using the backslash symbol (see the topic phases in the chapter on preprocessing).

Technically, the following is supposed to be possible, although in practice, the results appear to be implementation dependent.

// This is a comment\
   spanning two lines.